This invention relates to tape drives, and, more particularly, to tape drives which employ DC motors, wherein the tape drive is for mounting tape reels for rotation by the DC motors.
Tape, such as magnetic tape, provides a means for physically storing data which may be archived or which may be stored in storage shelves of automated data storage libraries, and accessed when required. As an archival medium, tape often comprises the only copy of the data.
The tape is typically thin so as to maximize the length of a tape stored on a tape reel or reels, and thereby maximize the amount of data that can be stored on the tape. If the tape drive does not function properly, the thin tape may be stretched or damaged, possibly causing loss of the data.
Tape drives frequently employ DC motors and feedback control systems with motor drivers for operating the DC motors, to produce well controlled motion parameters such as position, velocity, and tape tension. Such control systems are usually very complex, and the feedback control system may compensate for marginal components, hiding latent problems until a catastrophic failure occurs. At that point, if a user""s tape is in the tape drive and under control of the feedback control system, it is likely too late to protect the user""s data.
In accordance with the present invention, a verification system, logic, and a method are provided for verifying operational capability of a tape drive.
In one embodiment, logic is provided for operating a tape drive. The tape drive has a plurality of DC motors for rotating reels, a plurality of PWM motor drivers with DACs for operating the DC motors; and a plurality of Hall sensors for sensing the states of the DC motors. The logic operates the PWM motor drivers, and detects the Hall sensors. The logic:
operates the PWM motor drivers and verifies the on time duty cycle period and offset of the PWM motor drivers;
operates the PWM motor drivers in DISABLE mode and verifies DAC current reference and amplifier sense signals against positive and negative thresholds; and
operates the PWM motor drivers to rotate the DC motors in at least one direction, detecting the Hall sensors during the rotation, and verifies the Hall sensor state sequence of each of the DC motors for that direction; and
if the verification of the on time duty cycle period and offset for the PWM motor drivers, the verification of the DAC current reference and amplifier sense signals for the PWM motor drivers, and the Hall sensor state sequence for each of the DC motors, are all successful, the logic operates the PWM motor drivers to rotate the DC motors; and
accelerates the DC motors with a desired torque, and verifies the time of acceleration of each of the DC motors to a desired velocity;
verifies a computed velocity of each of the DC motors based on a measured velocity, to a reference velocity; and
verifies an actual rotation rate of each of the DC motors to a computed velocity thereof.
In another embodiment, additionally, upon detecting failure of any of the verification operations, the logic provides an error signal and identifies which operation failed.
In still another embodiment, the logic conducts the operations with the tape reels unmounted.
In a further embodiment, wherein the tape drive DC motors are bidirectional, the logic operates the PWM motor drivers to rotate the DC motors in a forward direction and in a backward direction, detecting the Hall sensors during the rotations, and verifies the Hall sensor state sequence of each of the DC motors for the forward direction and for the backward direction. In another embodiment, the DC motors are rotated subsequent to the verification of the on time duty cycle period and offset for the PWM motor drivers, and the verification of the DAC current reference and amplifier sense signals for the PWM motor drivers.
In a still further embodiment, the logic initially operates the PWM motor drivers in DISABLE mode, verifying PWM disable period, and determines the verification of the PWM on time duty cycle, and operates the PWM motor drivers in ENABLE mode, verifying PWM signal period and determines the verification of the offset.
For a fuller understanding of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.